The Federal Aviation Administration said on Wednesday that 43 flights into New Jersey's Newark Liberty International Airport were required to hold after drone sightings at a nearby airport on Tuesday, while nine flights were diverted.

The incident comes as major U.S. airports are assessing the threat of drones and have been holding meetings to address the issue.

The issue of drones impacting commercial air traffic came to the fore after London's second busiest airport, Gatwick Airport, was severely disrupted in December when drones were sighted on three consecutive days.

An FAA spokesman said that Tuesday's event lasted for 21 minutes. The flights into Newark, the 11th busiest U.S. airport, were suspended after a drone was seen flying at 3,500 feet over nearby Teterboro Airport, a small regional airport about 17 miles away that mostly handles corporate jets and private planes.

The Port Authority of New York and New Jersey, which operates Newark and Teterboro airports, as well as New York's John F. Kennedy International Airport, said on Wednesday that it hosted a working session with the FAA, the FBI and other law enforcement agencies last week "to review and enhance protocols for the rapid detection and interdiction of drones." It declined to discuss specifics for security reasons.

The Port Authority added that it is "committed to continuing our collaboration with the FAA and federal and state law enforcement partners to protect against any and all drone threats to the maximum extent possible."

The Chicago Department of Aviation said Wednesday it is working closely with the FAA and law enforcement "to ensure safe and secure operations at both O'Hare and Midway" but would not discuss drone preparations.

The FAA declined to comment on meetings with major airports, but said it has been in "close coordination" with security agency partners "to address drone security challenges."

The drone sightings at London's Gatwick Airport last month resulted in about 1,000 flights being canceled or diverted and affected 140,000 passengers.

The U.S. Congress last year gave the Department of Justice and Department of Homeland Security new powers to disable or destroy threatening drones after officials raised concerns about the use of drones as potential weapons.

United Airlines, the largest carrier at Newark, said on Tuesday that the impact to its operations had been minimal.

The FAA initially said it had reports of two drones on Tuesday evening, but it since clarified to say it had two reports of one drone in northern New Jersey airspace.

Earlier this month, the U.S. Transportation Department proposed rules that would allow drones to operate over populated areas and end a requirement for special permits for night use, long-awaited actions that are expected to help speed their commercial use.

There are nearly 1.3 million registered drones in the United States and more than 116,000 registered drone operators. Officials say there are hundreds of thousands of additional drones that are not registered.

The Federal Aviation Administration said on Wednesday that 43 flights into New Jersey's Newark Liberty International Airport were required to hold after drone sightings at a nearby airport on Tuesday, while nine flights were diverted.